The "spiral" refers both to the rise, this season, and to next season's inevitable fall.
It is my very firm opinion that a top 4 finish this season will come at the cost of complete and utter humiliation next season, in both the CL and the Prem.
In the CL, for example, even Leicester's fans cannot think that they, with their Wimbledon-esque brand of park-the-bus-then-hoof-it-up-the-park-for-Vardy football, is going to be anything other than the poorest grade of cannon-fodder for proper football teams?
Leicester would be better off starting out in the Europa League, and doing that for a few seasons, to prove that they have the credentials and consistency to mount an annual European campaign. It is not easy, as West Ham found out this season - and they were humiliated in the Europa ff!
The old saying is, that the faster they rise, the quicker they fall. Another is, the higher the climb, the harder the fall.
It's going to happen to Leicester City. We all know that, let's not pretend we don't. And sure - you can pay them all the patronizing plaudits you like, but that does not take anything away from my argument. They've capitalized in a season when so many teams have had their worst ever seasons! Well done to them, for that! But let's not pretend that this is anything other than a freak-season, particularly for Leicester City.